Generalize visible descendant dirty bits to prepare for more properties.

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 41b5b172576a9340a0619ceb6260876f6f83c6bb..c441436966b72bc192cdc55a7ef846ac2fa93cae 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -315,22 +315,17 @@ class CORE_EXPORT PaintLayer : public DisplayItemClient {
     return !hasVisibleContent() && !hasVisibleDescendant();
   }
 
-  // FIXME: hasVisibleContent() should call updateDescendantDependentFlags() if
-  // m_isVisibleContentDirty.
   bool hasVisibleContent() const {
     DCHECK(!m_isVisibleContentDirty);
     return m_hasVisibleContent;
   }
 
-  // FIXME: hasVisibleDescendant() should call updateDescendantDependentFlags()
-  // if m_isVisibleDescendantDirty.
   bool hasVisibleDescendant() const {
-    DCHECK(!m_isVisibleDescendantDirty);
+    DCHECK(!m_needsDescendantDependentFlagsUpdate);
     return m_hasVisibleDescendant;
   }
 
   void dirtyVisibleContentStatus();
-  void potentiallyDirtyVisibleContentStatus(EVisibility);
 
   bool hasBoxDecorationsOrBackground() const;
   bool hasVisibleBoxDecorations() const;
@@ -1073,7 +1068,7 @@ class CORE_EXPORT PaintLayer : public DisplayItemClient {
   bool requiresScrollableArea() const { return layoutBox(); }
   void updateScrollableArea();
 
-  void dirtyAncestorChainVisibleDescendantStatus();
+  void markAncestorChainForDescendantDependentFlagsUpdate();
 
   bool attemptDirectCompositingUpdate(StyleDifference,
                                       const ComputedStyle* oldStyle);
@@ -1135,7 +1130,7 @@ class CORE_EXPORT PaintLayer : public DisplayItemClient {
 
   unsigned m_isVisibleContentDirty : 1;
   unsigned m_hasVisibleContent : 1;
-  unsigned m_isVisibleDescendantDirty : 1;
+  unsigned m_needsDescendantDependentFlagsUpdate : 1;

[Xianzhu, 2016/12/01 17:59:32]

I'm not sure if the renaming is a good idea.

updateDescendantDependentFlags() updated both m_isVisibleContentDirty and
m_isVisibleDescendantDirty, so both of them seemed descendant (object and layer)
dependent flags.

If we want m_needsDescendantDependentFlagsUpdate cover both conditions (like in
this patch dirtyVisibleContentStatus unconditionally calling
markAncestorChainForDescendantDependentFlagsUpdate), we will do an extra level
of traverse into child layers in updateDescendantDependentFlags().

[chrishtr, 2016/12/01 18:05:22]

I could update the patch to try removing m_isVisibleContentDirty..
The new code for dirtyVisibleContentStatus will indeed cause recursion from the
root PaintLayer down to the one
whose visible contents status may have changed. I don't think that is a
significant problem, do you?

[Xianzhu, 2016/12/01 18:05:25]

Can this be m_childNeedsDecendantDependengFlagsUpdate?

[chrishtr, 2016/12/01 18:06:01]

Seem my comment in response to your one in PaintLayer.cpp about why it's not
just child any more.

[Xianzhu, 2016/12/01 18:07:03]

Removing m_isVisibleContentDirty SGTM.

[chrishtr, 2016/12/01 23:54:20]

Done.

   unsigned m_hasVisibleDescendant : 1;
 
 #if DCHECK_IS_ON()